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1.2 SERVO BLOCK (MN2DS0018MA : IC1501)
The servo block performs servo control, spindle motor control and seek control for focus, tracking, and traverse.
1.2.1 Focus Close
FODRV
RFENV
For both DVD and CD, the processing sequence after issuing a focus close command will be:
1. Measurement and optimization of a signal level
Drive the PU lens in the direction to get away from the disc first, and then drive it in the direction to get closer to the disc.
During the process, measure the signal levels of FE, AS, and RFENV when it passes the focusing point.
Optimize the signal levels for FE and AS (See
2. Focus pulling-in
Next, drive the lens in the direction to get away from the disc and detect pulling-in level of FE and AS.
Then, activate the Focus Loop Filter to pull in the focus (
3. Pulling-in check
Check the focusing with the signal levels of AS and RFENV (
Using a test mode focus search, you can check the signal levels of FE, AS, and RFENV as well as focus driving voltage.
1.2.2 Tracking Close
For both DVD and CD, the processing sequence after issuing a tracking close command will be:
1. Tracking brake
Measuring a 1/2 cycle of track cross, output a brake pulse if the cycle is within the specified range. In which direction
the brake pulse should be output is determined from the phase relation between OFTR and TKC signals (binarized
signal of TE). Once it is confirmed that the swinging of the lens against the disc has been successfully controlled,
stop braking and start pulling in. If the pulling-in conditions are not fulfilled within 10 msec after brake is output, stop
braking and start pulling in.
2. Tracking pulling-in
Process the tracking drive hold with an OFTR signal.
3. Pulling-in check
Check that track jump is less than the specified number within the specified period. The pulling-in check will time out in
8.4 msec and be retried upon receiving a command from the microprocessor.
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6
Close to Disc
Lens
Away from Disc
FE
AS
1
and
6
7
2
in the figure).
3
6
-
).
6
7
and
).
CX-3283
7
8
VHALF
Focusing Point
8
A
B
C
D
E
F
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